The most important is, what fits your head the best. There are different shell types for different heads. If you can find a place that has helmets in stock, you can get a good idea what brands fit you best. If you do use a motorcycle helmet, cyclegear has a ton of helmets in stock to try on and good prices. In autocross, track days and some racing the “M” snell is acceptable. More serious racing won’t allow it though. I use motorcycle helmets because I have been riding for over 20 years and I know what brands fit me. I can order them on line and know it will fit and be comfortable. My motorcycle race helmets are dot, snell and ece approved, which comply with the autocross and track stuff I do in the goblin. If I go further in racing, I’ll step up to auto type helmets, which are usually boring solid color helmets.